Frosty Start to Monday

It was chilly this morning. Many areas away from Lake Michigan had some patchy frost. Check out the lows from across the area.

Click on the image to enlarge it.

Many areas dropped down to the middle 30s. It stayed warmer near Lake Michigan thanks to the relatively warm waters acting like a heater. Away from the lake, many of you woke up to this:

A big thank you to Jake Stehli for the picture from Hartford this morning.

So if no temperatures dropped to freezing, how did we have a frost? Keep in mind, official temperature readings are taken 5.5 feet off the ground. Here is what an official weather instrument shelter looks like. Note the white color and holes for ventilation. Most bank clock thermometers are wrong because the instrument is placed in the sun without the proper shelter.

 On a clear and calm night like last night, the temperatures can actually cool below freezing near the surface and on other surrounding objects…such as the roof in the picture above. To get frost, you still must have a temperature dropping to freezing or below. Frost is not frozen dew, but water vapor changing directly to ice. This is called deposition. Usually temperatures get coldest at night in low-lying areas as the cold air pools at the bottom of a valley.

No frost expected tonight, but it will still be chilly. Nice weather in Chicago for a Packers victory. Game time temperatures will be in the middle 50s with light winds.

In the extended forecast, I have dropped the temperatures for the weekend. It is looking like a pretty good blast of cold will move in. Our first freeze is possible.

Thanks for reading and have a great night. Go Pack Go!

Mark

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2 Responses

  1. I had a surprise this morning when I woke up to discover a heavey frost on the low-lying section of lawn to the east of the house. I didn’t catch any forecasts yesterday so was unaware of frost potential for last night. It didn’t take long to disappear once the sun came up. I think we had a lot of local frost in the area this morning. I live in NE Dodge between Brownsville and Lomira.

    Not liking the weekend forecast…not sure if I’m ready for a freeze yet, although I guess it’s that time of the year.

    • Hey, Cliff,

      Frost was in the forecast. Frost advisory was in effect for Dodge county. Hope you did not lose any flowers.

      Mark

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